A photographic technique of image duplication has conventionally been known, which uses a photosensitive composition comprising a mixture of a compound having one or more addition-polymerizable ethylenically unsaturated bonds, a photopolymerization initiator, and optionally an appropriate binder having film-forming ability and a heat polymerization inhibitor. Examples of this technique are described, e.g., in U.S. Pat. Nos. 2,927,022, 2,902,356, and 3,870,524. As described therein, this kind of photosensitive composition undergoes photopolymerization upon light irradiation and thus cures to become insoluble. Consequently, a desired cured image can be formed from the photopolymerizable composition, as described in those U.S. Patents, by forming the photosensitive composition into an appropriate film, irradiating the film with light through a negative bearing the desired image pattern, and removing the film only in the unexposed areas with an appropriate solvent (hereinafter simply called development). This type of photosensitive composition is extremely useful as a material for producing printing plates, etc.
Since the single use of the compound having one or more addition-polymerizable ethylenically unsaturated bonds does not have sufficient photosensitivity, it has been proposed to add a photopolymerization initiator thereto in order to heighten the photosensitivity. The photopolymerization initiators which have been used in this application include benzil, benzoin, benzoin ethyl ether, Michler's ketone, anthraquinone, acridine, phenazine, benzophenone, and 2-ethylanthraquinone. However, use of these photopolymerization initiators has a drawback that the resultant photopolymerizable compositions have reduced response in curing and hence necessitate a prolonged period for image-wise exposure in image formation, and even slight vibration in the operation makes it impossible to attain satisfactory image quality in reproducing a fine image. Furthermore, since the amount of irradiation energy of the light source for exposure should be increased, it is necessary to account for a large amount of the resultant heat irradiation. In addition, there is a further problem that the heat is apt to cause deformation and denaturation of the film of the composition.
On the other hand, investigations are recently being made on the enhancement of sensitivity to ultraviolet rays and techniques for forming an image with a laser. Image-forming techniques based on the UV projection exposure method, direct laser platemaking, laser facsimile, holography, etc. are in a stage in which they can be put to practical use. High-sensitivity photosensitive materials capable of coping with these techniques have hence been desired, and are being developed.
In particular, a photopolymerizable composition having an oxime ether compound is proposed in JP-A-8-202035 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") as a photopolymerizable composition having high sensitivity and excellent storage stability.
Use of that oxime ether compound is preferred in that it improves sensitivity as the addition amount thereof increases. However, the resultant composition tends to give a film which is brittle due to the oxime ether compound present therein. Consequently, no fully satisfactory photosensitive material has been obtained so far.